The present invention relates generally to loading ramp assemblies and cargo trucks having loading ramps, and more particularly a loading ramp which has low profile side rails for convenient storage between the cargo box and the truck frame of a cargo truck.
Cargo trucks having loading ramps are well-known in the art. One typical design for the ramps is to provide two long C-shaped sills between the frame of the truck and the cargo box. The sills are mounted so that the legs of the sills are facing each other. The ramp fits within the sills. The ramp itself consists of horizontal cross members which form the ramp floor between two side rails. To move the ramp to a loading position, an operator pulls the ramp out the back of the truck until it is free from the sill. Typically there is some means provided to hook the front end of the ramp to the deck of the cargo box.
Generally, past designs have effectively allowed for the storage of the ramp on the truck and have been sufficient to aid in the loading and unloading of the cargo box. However, some problems do exist with the ramps disclosed in the prior art. The side rails were required to be of a large height in order to have sufficient structural modulus to prevent excessive deflection or collapse of the ramp upon the application of a load during loading and unloading. This high profile of the side rails means that the ramp takes up a lot of space during storage. Typically this space was created by raising the floor of the cargo box. A raised cargo box can be undesirable because it can be more difficult to load, can cause increased wind drag during transportation, can raise the center of gravity, and can cause clearance problems at the top of the box.
Also, because of the height of the side rails, the deck of the cargo box was typically set directly on to the long sills. This meant that the cross members that supported the deck had to be terminated at the sills. This created three different cross members out of a single cross member that went all the way across, thereby weakening the deck. It also meant that the ramp assembly could only be used with specially adapted cargo boxes, without raising the floor of the cargo box. The difficulties encountered in the prior art discussed above are substantially overcome by the present invention.